1. Field of the Invention
The present invention generally relates to medical infusion systems for delivering therapeutic fluids to a patient, and more particularly relates to a fluid reservoir used as part of an infusion system or device for delivering such therapeutic agents into the body of a medical patient.
2. Description of the Prior Art
Many therapeutic fluids, for example, medicines, local anesthetics and the like, must be delivered to a patient for extended periods of time either subcutaneously or intravenously. The rate of the delivery of the therapeutic fluid must be well regulated to ensure a safe and efficacious treatment. Conventionally, this requires the attention of a medical professional who can monitor the fluid delivery on a regular basis.
Infusion pumps and catheters are frequently used in conjunction in an infusion system to deliver such therapeutic fluids to a patient for many purposes, for example, to alleviate postoperative pain, and chemotherapy. However, conventional systems do not address a number of significant functional or user interface issues.
Existing infusion devices require a series of preparation steps typically performed by a nurse or surgeon that may be easily confused by the user. For example, U.S. Pat. No. 4,769,008, which issued to Stephen R. Hessel, and U.S. Pat. No. 5,080,652, which issued to Gregory E. Sancoff et al., the disclosures of which are incorporated herein by reference, disclose infusion devices which require the user to connect a syringe to an input port and not to the output port after securing a clamp. If the syringe is attached to the incorrect end and pressure is applied, the device will malfunction, for example, an incorporated filter may be damaged (e.g., the filter media may pop). Furthermore, if the clamp is not activated properly, the device will not function properly, as fluid may be expelled from the device prematurely.
Many existing infusion devices require that the user perform difficult steps. For example, the aforementioned U.S. Pat. No. 5,080,652 to Sancoffet al. discloses an infusion device that requires the user to balance the device atop the filling syringe in a precarious position while the user applies a significant amount of hand force to the filling syringe, thereby creating a situation where the user may lose control of the device and the filling syringe. This may result in the device falling on the floor or in breaking the device. As another example, U.S. Pat. No. 4,909,790, which issued to Hajine Tsujakawa et al., the disclosure of which is incorporated herein by reference, describes a liquid infusion device having a stop-cock to regulate the flow into and out of a pressurized fluid reservoir, wherein the user must skillfully manipulate the stop-cock while retaining significant pressure on the filling syringe, thus requiring significant skill or strength on the part of the user to perform the steps required for using the infusion device.
Many other conventional infusion devices, such as most medical fluidic “needle-free” devices, utilize standard luer fittings for performing fluidic connections. Many infusion devices, for example, the On-Q™ PainBuster™ postoperative pain relief system manufactured by I-Flow Corporation of Lake Forest, Calif., and the Infusor™ infusion system manufactured by Baxter Healthcare Corporation of Round Lake, Ill., incorporate at least two luer fittings. The ubiquitous use of luer fittings has led to the accidental connection of unrelated medical devices, which may cause a patient further health problems or even death.
Many conventional infusion devices regulate flow commencement and termination using a simple plastic clamp, such as on the aforementioned I-Flow's On-Q™ PainBuster™ postoperative pain relief system, or a stop-cock, as disclosed in the aforementioned U.S. Pat. No. 4,909,790 to Tsujakawa et al. Often, a patient inadvertently ceases the delivery of a therapeutic fluid from the infusion device by accidentally closing the clamp, for example, by sitting on it. As a result, some surgeons and nurses have begun the practice of removing the clamp from the infusion device. But, many clamps are not designed to be removed, and this action could potentially damage the infusion device, for example, by cutting the device's tubing.
Other known infusion devices often must hold large volumes of fluid, sometimes up to one-half liter. Yet, it is the desire of patients who use the infusion devices that the infusion devices be unobtrusive, having a low profile and are “pocket-size”. While some conventional infusion devices address this need, for example, the automatic injection device and reservoir disclosed in U.S. Pat. No. 5,957,895, which issued to Burton H. Sage et al., the disclosure of which is incorporated herein by reference, the inventors of the present device are unaware of any low profile devices that utilize an elastomeric bladder for the dual purpose of a) storing therapeutic fluids and b) providing system pressure.
Several currently marketed infusion devices incorporate elastomeric bladders that are generally affixed to a rigid structure using securing devices such as plastic or rubber rings, for example, the Accufuser™ disposable infuser manufactured by McKinley Medical, LLC of Wheat Ridge, Colo. or the aforementioned I-Flow's On-Q™ PainBuster™ postoperative pain relief system, or heat shrink tubing, for example; the aforementioned Baxter Infusor™ infusion system. In order to maintain structural integrity and to prevent the inflated bladder from displacing the securing device or to prevent the securing device from damaging the bladder, the bladders are provided with a very thick wall to allow for a deeper seat for the securing device. This thick wall requires that the user supply a higher pressure to inflate the bladder than would be necessary if an improved securing mechanism were utilized that did not require the use of a thick tube. Many users of existing devices have complained that these existing devices are difficult to inflate because of the strength required to impart inflation on the elastomeric bladder.